JPH04292896A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To miniaturize a device, reduce the cost, and improve the performance and safety by utilizing a current transformer among element parts constituting a discharge lamp lighting device. CONSTITUTION:A discharge lamp lighting device is formed of a DC power source 1, a high frequency inverter 2 for converting the output of the DC power source 1 to a high frequency voltage, a series resonance circuit connected to the high frequency inverter 2, a discharge lamp 5 connected to the series resonance circuit, and a current transformer T1 for detecting the abnormal state of the discharge lamp 5 such as the life end. The current transformer T1 is operated as a stabilizer for limiting the lighting current of the discharge lamp 5, the output voltage of the current transformer T1 is also rectified to detect an excess current, the operation for stopping an oscillating circuit 7 is performed, the voltage is supplied to a driving circuit 6 and the oscillating circuit 7 with the rectified voltage as a DC power source after start, and the DC power source 1 is cut at the time of detecting the excess current.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a discharge lamp lighting device for lighting a discharge lamp using a high-frequency inverter, and in particular to a current limiting element of a discharge lamp, abnormality detection at the end of a discharge lamp's life, and control circuitry. Relates to devices that supply and cut off DC auxiliary power.

0002

[Prior Art] In order to detect abnormal current at the end of the lamp's life in this type of discharge lamp lighting device, conventionally a current transformer is provided in a part of the discharge circuit in addition to an impedance element (ballast). The secondary output voltage was rectified and used as a signal to stop oscillation of the oscillator. On the other hand, when controlling a DC power supply for an oscillator, etc., when the power is turned on (starting), the commercial power supply on the input side is converted to step-down DC power using a transformer, or the DC power supply that is directly rectified from the commercial power supply is divided into voltage branches from the main circuit. After startup, the output voltage of the auxiliary winding attached to the oscillation transformer was supplied.

However, according to this conventional example, an impedance element (ballast) and a current transformer are used, and an auxiliary winding is added to the oscillation transformer, which increases the number of windings and increases the size of the device. , it has the disadvantage of increasing complexity.

0004

[Problems to be Solved by the Invention] The present invention is directed to a high-frequency inverter and other component parts constituting a discharge lamp lighting device.
The windings, which account for a large proportion of both volume and cost, have been simplified to make the device more compact, reduce costs, and improve performance and safety.

[0005]

[Means for Solving the Problems] A discharge lamp lighting device of the present invention comprises a DC power source, a high frequency inverter that converts the output of the DC power source into a high frequency voltage, a series resonant circuit connected to the high frequency inverter, and a series resonant circuit connected to the high frequency inverter. It consists of a discharge lamp connected to a series resonant circuit and a current transformer that detects abnormal conditions such as the end of the life of the discharge lamp.
It operates as a ballast that limits the lighting current of the discharge lamp, and rectifies the output voltage of the current transformer.
Detects overcurrent, performs an operation to stop the oscillation circuit, and converts the rectified voltage obtained by rectifying the output voltage of the current transformer,
The feature is that the DC power supply after startup supplies power to the drive circuit, oscillation circuit, etc., and when an overcurrent is detected, the DC power supply is cut off. It is characterized by the provision of a current transformer that has three functions: impedance), abnormality detection current transformer, and auxiliary power supply transformer.

[0006]

[Operation] With the above configuration, one current transformer on the circuit limits the discharge current, detects abnormal current,
Supply and cut off DC auxiliary power.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the discharge lamp lighting device of the present invention will be described below with reference to the drawings.

FIG. 3 is a basic circuit diagram of a conventional discharge lamp lighting device, which is composed of a DC power source 1, a high frequency inverter 2, an inductive element 3, a capacitive element 4, and a discharge lamp 5. Using 4 series resonant circuits, starting, dimming,
Frequency control is performed for abnormality detection procedures.

Hereinafter, the circuit portions that characterize the present invention will be described in detail based on the circuit diagram of the embodiment of the present invention shown in FIG.

The DC power supply 1 is a DC power supply obtained by rectifying a commercial power supply, and the high frequency inverter 2 is controlled by an input signal of a drive circuit 6 driven by an oscillation circuit 7.

The oscillation circuit 7 is, for example, a TL-49 manufactured by TI.
The oscillation frequency of an integrated circuit (IC), such as a type 4 IC, is determined by a capacitor (not shown) and a resistor (not shown) connected thereto.

The drive circuit 6 is a drive circuit that converts the output of the oscillation circuit 7 into a drive signal for a field effect transistor (FET) or the like of the high frequency inverter 2, and includes a pulse transformer and the like. The high frequency inverter 2 is a switching circuit using FETs and the like.

When the commercial power is turned on, the start timer 8 turns on the transistor Tr1, charges the capacitor C2, and supplies the auxiliary power +B, and after a certain period of time turns off the transistor Tr1 and at the same time turns on the transistor Tr2.
This switching device serves as a timing timer for turning on the current transformer (CT) T1 and supplying the secondary output power of the current transformer (CT) T1 as an auxiliary power supply +B.

The operation of the above configuration will be explained below.

When the power is turned on, the DC power supply 1, which is a rectified and smoothed commercial power supply, is turned on by the start timer 8.
1 is turned ON, the capacitor C2 is charged, the auxiliary power supply +B is supplied to the oscillation circuit 7 and the starting circuit 6, and the switching operation of the high frequency inverter 2 is started.

The primary side of the current transformer T1, which is a switching element (FET etc.) and the inductive element T11, the discharge lamp 5
Sufficient preheating current and starting voltage are applied by the series resonant circuit constituted by both filaments f1 and f2 and the capacitive element 4, and the lamp starts and lights up. A high frequency voltage is generated on the secondary side of the current transformer T1 by the primary side of the current transformer T1 due to the current during preheating and lighting. At this time, the current transformer T according to the oscillation frequency of the oscillation circuit 7
With an impedance of 1, the discharge lamp 5 is controlled to a predetermined current depending on a mode such as full light or dimming. The secondary output VS of the current transformer T1 is made into a direct current through the rectifier D1, and is charged to the capacitor C1, and the voltage VC1 of the capacitor C1 rises to a voltage corresponding to the primary current of the current transformer T1.

On the other hand, the terminal voltage VC1 of the capacitor C1 is divided into resistors r3 and r4, inputted to the comparator section of the oscillation circuit 7, and compared with the reference voltage VREF.
Oscillation is stopped only when an abnormally excessive current occurs, such as at the end of the service life of the device.

In this case, it is also possible to increase the oscillation frequency, increase the primary impedance, and reduce the current without stopping the oscillation, thereby bringing the discharge lamp 5 into a dimmed state.

Next, after a certain period of time, the switching operation of the starting timer 8 turns off the transistor Tr1 and turns on the transistor Tr2 at the same time, charging the capacitor C2 from the DC power supply 1 via the resistor r5. This is done by using the secondary output voltage of the current transformer T1, the current flowing from the DC power supply 1 through the resistor r5 decreases, the heat generated by the resistor r5 also decreases, and the efficient supply of auxiliary power +B is achieved. can be maintained.

Therefore, the shunt resistor r5 is small and inexpensive, and the heat generated by the lighting device can be reduced. Furthermore, when the oscillation is stopped due to the above-mentioned overcurrent detection, the auxiliary power supply +B is also cut off, improving safety.

[0021] The same procedure can be carried out in the case where there are a plurality of discharge lamps. For example, as in another embodiment shown in FIG. 2, a current transformer T1 and a current transformer T2 are provided in the lighting circuit of each of the two discharge lamps 5 and 10, and each secondary output current is transmitted through a resistor r1, a resistor r2, and a rectifier. D1 and rectifier D2
may be connected in parallel and connected to one end of the capacitor C1 and the resistor r3. In this case, if an abnormal current occurs in one or both of the discharge lamp circuits, the terminal voltage of the capacitor C1 increases, and the abnormal voltage can be detected by the voltage dividing resistors r3 and r4.

[0022]

[Effects of the Invention] Since the present invention is configured as described above, it functions as a ballast to control the discharge current, detects overcurrent at the end of the discharge lamp's life, and provides assistance after starting. A single current transformer (CT) can serve both to generate the supply voltage for the power source and to cut off the auxiliary power source in the event of an abnormality, making it possible to downsize the device, reduce costs, and improve safety.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an embodiment of the discharge lamp lighting device of the present invention.

FIG. 2 is a circuit diagram of another embodiment.

FIG. 3 is a basic circuit diagram of a conventional discharge lamp lighting device.

[Explanation of symbols]

1 DC power supply 2 High frequency inverter 4, 9 Capacitive element 5, 10 Discharge lamp 6 Drive circuit 7 Oscillation circuit 8 Start timer T1, T2 Current transformer

Claims (1)

[Claims] 1. A DC power source, a high frequency inverter that converts the output of the DC power source into a high frequency voltage, a series resonant circuit connected to the high frequency inverter, a discharge lamp connected to the series resonant circuit, and a discharge lamp connected to the series resonant circuit. It consists of a current transformer that detects abnormal conditions such as the end of the lamp's life.The current transformer operates as a ballast that limits the lighting current of the discharge lamp, and rectifies the output voltage of the current transformer to prevent overcurrent. The rectified voltage obtained by rectifying the output voltage of the current transformer is used as a DC power source after startup to supply power to the drive circuit, oscillation circuit, etc. when an overcurrent is detected. A discharge lamp lighting circuit characterized by cutting off the DC power supply.